RAMS seminar. Vibration by Viggo Pedersen

Transcription

1 RAMS seminar Vibration by Viggo Pedersen

2 Vibration and Machine Learning Features Label Predictive maintenance Probability of failure Remaining useful life Machine learning when: Complex process Large amounts of data High cost equipment Failure impact high (costs, life, etc.) 2

3 Vibration and Machine Learning A Bently Nevada Rotor Kit is used for the experiments. Max rotor speed rpm, can be adjusted in infinite steps. Analog signal (charge) emitted from Kistler piezo electric accelerometers mounted on the rotor kit is proportional to the vibration level. A discrete-time signal sampled over a period of time is representing the vibration level of rotating machinery in the time domain. Sample frequency is 5000 points in one second. One sample a second. 3

4 Analog (raw) signal WPD signal - coefficient's Feature Extraction Energy features numbers indicate energy level Three types of failures are introduced: bearing looseness, axel friction, and unbalance. For each type of failure, the vibration signals and rotating speed was measured by means of accelerometers (x,y,z) and proximity probe.

5 Classification of measurements Supervised learning 5

6 Conclusions The new method introduced in this paper is able to detect the failures introduced on the rotor kit with high accuracy (ISO ). Only one sample of 784 randomly selected samples is misjudged. 6

7 Vibration analysis A machinery set up consists of several components Each component will have a vibration footprint at a certain frequency (using FFT to transform analog signal in time domain to frequency domain) A change in frequency «amplitude» indicates something is wrong and the root component of the wrong 7

8 WHAT IS VIBRATION? Simply put: The motion of a machine or its part back and forth from its position of rest The displacement X of a spring mass system with respect to time can be expressed: X=X 0 sinωt X 0 = max displacement ω =2 * π * f, f=frequency [Hz] t= time [seconds] Velocity = dx dt Acceleration = d(velocity) dt 8

9 Shock Pulse Method The SPM method is used to monitoring roller and ball bearings. Two metal surfaces in contact with each other while in motion will generate a shock wave on impact this wave travels through metal in the ultrasonic range and is around 36 khz. Reference : SPM 9

10 Vibration signals FFT is most frequently used in vibration analysis signal transformation 10

11 Vibration signals Mobius Institute 11

12 Vibration patterns -unbalance Mobius Institute 12

13 Vibration patterns - misalignment Mobius Institute 13

14 Vibration patterns Resonance Mobius Institute 14

15 Vibration amplitude can be measured 3 ways Mobius Institute 15

16 The 3 amplitudes Displacement the distance a mass moves Velocity how fast the mass is moving at any given point Acceleration the rate of change of velocity 90 deg. apart Displacement measured in micron (μm) proportional to stress [ N mm 2] Lower speed machines (below 600 rpm) Proximity sensors Velocity measured in [ mm ] proportional to fatigue [ strain cycles] sek Accelerometers ( beware measurement range) Acceleration measured in [ m s 2] proportional to forces within a machine[n] High speed machines ( rpm and above) Accelerometers 16

17 Proximity sensor Magnetic field is set up by the electrically powered sensor. The magnetic field changes as the axel comes nearer to the probe. PIB 17

18 Piezoelectric element Accelerometer Pressure added to element changing electric charge PC control 18

19 19 Sensor Mounting

20 Evaluation of machine condition Determining harmful vibration level is often based on ISO 2372 or Vendor recommendations Owner experience Consultants advice 20

21 Thanks for listening Referanser: Bye, Per I. (2009). Vedlikehold og driftssikkerhet. Trondheim 21